A memory system may include: a memory device including a plurality of memory blocks which includes memory cells supporting a two-or-more-level cell (XLC) mode and a single level cell (SLC) mode; and a controller suitable for managing data of the memory device and controlling the memory device, wherein, when memory usage of the memory device is greater than or equal to a first threshold value, the controller selects one or more free memory blocks as one or more victim memory blocks, switches a mode of each victim memory block to the XLC mode, and moves data stored in a source memory block to the one or more victim memory blocks, wherein the source memory block, among the plurality of memory blocks, has data stored therein driven in the SLC mode.